This invention relates to balloon catheters, such as those used in angioplasty and stent delivery, and in particular to magnetically navigable balloon catheters.
Balloon catheters, i.e. catheters have an expandable balloon adjacent their distal ends have found a number of medical applications. For example in angioplasty, the catheter is navigated into a partially closed blood vessel and the balloon is inflated both to stretch the vessel and to compress the atheromatous material on the vessel wall, thereby widening the vessel to increase blood flow. Balloon catheters are also used in a similar procedure in which a stent is placed in the blood vessel to help keep the vessel open. The catheter with a compressed stent over the balloon is navigated to the desire site of placement, and the balloon is inflated to expand the stent in the vessel. These and other procedures employing balloon catheters are value and important procedures that can extend lives and improve quality of life, but whose use, however, is limited by the difficult of navigating the catheters in the small and partially blocked vessels. The balloon, and particularly a balloon and stent, can be very difficult to navigate using conventional means. The sharp changes in flexibility of the catheter, particularly at the proximal and distal ends of the balloon make it difficult to direct the catheter into certain. To overcome some of the navigation issues, manufacturers of stents have lowered the amount of metal contained in a stent in order to make them more flexible at the possible expense of optimum vessel scaffolding and coverage. A tool that can improve the navigability of less flexible stents is desirable.
One of the embodiments of the invention is a self expanding stent. This is a stent that automatically expands when delivered to the site of the occlusion. These are typically constrained by a sheath that is retracted once the stent has been delivered to the correct location. Retraction of the sheath then allows the stent to reach its normally open configuration and keep the vessel open.